CFD Online Discussion Forums

CFD Online Discussion Forums (
-   CFX (
-   -   Jet penetration problems (

Ahmad May 4, 2006 10:40

Jet penetration problems
I am running a cold jet simulation from a round inlet and I'm having problems with the penetration of the injected gas in the computational domain. The domain consists of a 5 degree-wedge of a cylinder having a height of 150 mm and a radius of 30 mm. The radius of the inlet is 0.55 mm. The injected gas is CH4 (P=3 atm T=300 k) and the domain is initialized with air (P=1 atm and T=300k). For the boundary conditions, I'm using a pressure subsonic inlet, symmetry for the front and back surfaces and openings for the remaining surfaces. My results are less by a factor of 10 than the experimental and correlated data sets. My objective is to collect the mixture fraction (and its variance) of the injected gas. Any advice is highly appreciated. Thank you.

Joe May 5, 2006 02:35

Re: Jet penetration problems
Did you check the classic questions?

Ahmad May 5, 2006 11:36

Re: Jet penetration problems
I didn't get it. what do you mean? My main problem is that the jet is not penetrating enough in the domain... I might have forgotten to set some paramaters or missed some important details, especially concerning compressibility. is it controllable or is the solver set by default to deal with compressible flows?

Quest May 5, 2006 12:13

Re: Jet penetration problems
Maybe set the reference pressure to 0 atm. if its 1 atm every pressure level you set is 1atm more.

Ahmad May 5, 2006 12:17

Re: Jet penetration problems
My reference pressure is 1 atm. Given a pressure ratio of 3/1, the relative pressure of the injected gas (CH4) is 2 atm and the initial pressure in the domain (consisting of Air at t = 0 s) is 0 atm.

dh May 6, 2006 07:22

Re: Jet penetration problems
You will be running incompressible flow by default. To turn on compressibility, you should enable the Total Energy model. You need to use materials that are set up as an Ideal Gas or Real Fluid. You may also model compressible flow for a General Fluid whose density is a function of pressure.

Ahmad May 6, 2006 11:51

Re: Jet penetration problems
In my simulation, the "Total Energy" option is enabled in "Fluids Models" and the viscous work term is included. About modelling a compressible flow with density being a function of pressure, how is this done? Thanks...

All times are GMT -4. The time now is 00:44.